Engines : H and K-Series prototypes

The A-Series may have been almost immortal by the early 1970s, but it did not stop the company developing alternatives. Here we describe the H and K-Series prototypes which were designed for the ill-fated ADO74 supermini.

Transmission-in-sump could have had a future

Any AROnline readers who have read the Metro development story might recall that, back in the mid-1970s, the decision was made to build a car around a developed version of the A-Series engine and transmission. This was instead of designing a new power unit.

Both the ill-fated BMC 9X and ADO74 had been destined to have an all-new engine. Eminent Engineer Roy Brocklehurst described how the company were, ‘tickled pink with its NVH performance’, once the upgrades had been made which turned it into the A-Plus.

A new decade, a new engine

However, what about the engine that had been passed over when the ADO74 was scrapped? Obviously, at the time of the Metro launch in 1980, the company’s Directors tended to describe the K-Series engine as not being a great enough step over the A-Series to justify the cost (and, in essence, they were correct to do so, as Bill Appleby and his team knew what they were doing when they designed the A-Series), but that is to undermine what Austin-Morris engineers achieved with the H and K-Series engines.

In 1972, when the ADO74 programme began, the engine which was then intended to be used was called the H-Series and that employed the transmission-in-sump layout. As the ADO74 was initially devised as a straight replacement for the Mini, the capacity was limited to a maximum of 1000cc.

Transmission-in-sump, like its predecessor

The integrated engine/gearbox was designed for ease of servicing, and access was achieved by removing the single sump – the clutch was also similarly easily accessible through its cover. In one fell swoop, this clever design overcame the criticism of the A, B and E-Series engines that they were difficult to service. This design also did not sacrifice the undeniable packaging advantage of the transmission-in-sump system.

Ray Battersby, who was one of the H and K-Series designers, said: ‘Harry Webster was the engineering dictator and control freak of all we did in the engineering block. His design strictures were designed to prevent any future boring and stroking of the cylinder block.

‘The very narrow cylinder bridge width would also cause much anguish by Coopers and Klingers, who were each tasked with producing a cylinder head gasket design able to withstand the heat, the fretting and general hostility in this bridge area without leaking between adjacent cylinders.’

So, what did the H-Series engine look like?

According to Battersby, ‘the first H-Series engine ran on schedule on the test bed in December 1971.’ It was a 1000cc ‘dedicated’ engine that had been laid-out by Harry Webster in a planning document, released on 24 September 1970. It was an extremely compact unit which featured Siamesed bores (just like the E-Series engine) and an OHC cylinder head with bucket tappets (see Battersby’s comments, above). The distributor was mounted directly on the end of the belt-driven camshaft and the water pump and alternator were driven from the crankshaft.

The oil-pump was also crankshaft mounted. A two-shaft transmission layout was designed, and this was driven by helical spur gearing. This was carried in a housing integral with the rear transverse face of the cylinder block. The clutch was of conventional design, and this had a separate cover.

According to Battersby, it was ready to go. ‘One engine, after running in, was subjected to a 400-hour Endurance Test, which started on 11 January 1972 and was completed on 11 February 1972,’ he said. ‘This gruelling test was the equivalent of running on the road for 26,000 miles with the engine running at full throttle and full load for over half of the time. The full test comprised of 69 cycles (each of 5:50 hours).’

Why was the H-Series dropped?

In total, four or five H-Series prototypes were built, and were run for between 200 and 800 hours on the test bed and 25,000 miles on the road in ADO16 mules. But the H evolved into the K-Series engine, when the ADO74 grew, and the limitations of the 1000cc upper limit became too much for the larger car.

In essence, the K-Series differed from the H in three areas: it had a larger engine capacity, the gearbox featured five ratios and more of it was inclined steeply to the rear to improve packaging.

The new two-shaft, five-speed gearbox was carried in a hefty housing, cast integrally with the rear face of the cylinder block (see diagram above) and, like its predecessor, the engine and gearbox were closed off underneath with a single pressed steel oil pan. As before, servicing was made relatively easy by this layout – since the gearbox internals and crankshaft could be released by the removal of simple half-bearing caps.

So, what did the K-Series engine look like?

The K-Series evolution was to have been the definitive ADO74 power unit, and was designed in two forms: the 900/1100 version, and later 1100/1300. This change in policy was down to Harry Webster deciding to hedge his bets about the new supermini’s engine range make-up. It was laid down in late 1972.

Like the H-Series, the 900/1100cc K-Series was canted back, but according to Battersby, ‘its cylinder bank was also canted back relative to the sump joint-face. Its doubly laid back cylinders allowed the unit to fit beneath the very low bonnet-line of ADO74.’

However, as Battersby put it, ‘something gave Harry Webster the jitters, because no sooner had we started designing the K-Series 900/1100 than he issued another edict, changing the capacity range yet again. This led to the birth of the K-Series 1100/1300cc project. Due to the continuing stipulation in Webster’s ‘Design Considerations’, neither the bore nor the stroke of the K-Series 1300cc engine could be increased.’

The H and K-Series prototypes are canned

The ADO74 project was then dropped and its engine died with it. The legacy of these engines was their inspiration within the design of the A-Series OHC and O-Series OHC engines, whose cylinder heads and valvegear bear the hallmarks of their ancestry.

According to Battersby, good progress was made on the H-Series before it grew up to become the K. ‘I believe that within this ‘family’ of engines (H-1000, K-900/1100, K-1100/1300), only the H-Series was ever built and only the H-Series was ever run on a testbed and fitted to a vehicle for road testing. I seem to recall that many of the K-1100/1300 parts were manufactured, but not assembled by the time the project was scrapped in 1974.’

Would the story of the Metro have been any different with this engine in place? Probably not, as the car was a success, and a long-lived one at that, with its A-Series engine.

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21 Comments

I dare say the A+ did perform well. But the Metro/Maestro where being launched just as Ford and GM/Vauxhall where ditching their Iron headed push rod lumps for the CVH and Family 1/2 respectively. Alloy heads, Overhead Cams, hydraulic tappets and power outputs for the standard engines that exceeded those for their predecessor “GT” versions. Slotting a 30 year old pushrod Engine into ARG’s new cars sent out all the wrong messages.

The E-Series transmission with its remote cable-operated gear-shift was berated by the press from its launch for indistinct changes that felt like pushing the gear stick through a box of loose ball-bearings. Remember that at that time, the mass-produced Ford gearbox fitted to the Escort, Cortina etc was absolutely superb; slick, short movements and strong with large synchromesh hubs. It was used by many track racing cars. A brilliant gearbox design.

No, no no. The E-Series box was a gonner for that reason alone.

Then there was the crippling effect of designing an engine around an alien component. The H and K-Series engines were crippled enough by board members who specified its minutiae even before a designer had sharpened his first pencil.

We engine designers at that time worked literally arm in arm with our colleague transmission designers who were all extremely proficient. The problem for both teams (about 25 designers in each team) was a company ham-strung for cash and a management team who were way out of their depth.

Given your involvement as a designer of the H/K-Series engine, was wondering whether you can clarify some things regarding this project?

Did the H/K-Series share anything with the A-Series as one or two books have suggested a connection with the A-OHC?

How did the H/K-Series compare with the A-Plus and A-OHC (assuming the latter is completely unconnected with the H/K unit)?

What was the minimum capacity of the H/K-Series units and had the project been given the green light, how much further could the later K-Series engine capacity have been increased by beyond 1300cc upper limit?

Collectively, these strictures were designed to prevent any future boring and stroking of the cylinder block. The very narrow cylinder bridge width would also cause much anguish by Coopers and Klingers who were each tasked with producing a cylinder head gasket design able to withstand the heat, the fretting and general hostility in this bridge area without leaking between adjacent cylinders.

Two further designers joined the team between January and March 1971. The first H-Series engine ran on schedule on the test bed in December 1971.

K-SERIES 900/1100 – Despite Webster’s steely determination to have a ‘dedicated’, ham-strung 1000cc engine, early in 1972, he decided to hedge his bets. He now wanted it to be a dual-capacity design encompassing 900 and 1100ccs.

This 900/1100 engine became the basis for the K-Series whose entire power unit – like the H-Series – was canted back on installation. However, its cylinder bank was also canted back relative to the sump joint-face. Its doubly laid back cylinders allowed the unit to fit beneath the very low bonnet-line of ADO74.

K-SERIES 1100/1300 – But…but something had clearly given Harry Webster the jitters because no sooner had we started designing the K-Series 900/1100 than he issued another edict, changing the capacity range yet again. This led to the birth of the K-Series 1100/1300ccs project. Due to the continuing stipulation in Webster’s ‘Design Considerations’, neither the bore nor the stroke of the K-Series 1300cc engine could be increased.

But it didn’t matter anyway. The entire ADO74 project was dropped including work on its engine. I believe that within this ‘family’ of engines (H-1000, K-900/1100, K-1100/1300) only the H-Series was ever built and only the H-Series was ever run on a test-bed and fitted to a vehicle for road testing. I seem to recall that many of the K-1100/1300 parts were manufactured but not assembled by the time the project was scrapped in 1974.

The legacy of these engines was their inspiration within the design of the A-Series OHC and O-Series OHC engines, whose cylinder heads and valve-gear bear the hallmarks of their ancestry.

In his excellent book ‘The A-Series Engine’, Graham Robson says that the H-Series ran for 200 hours on the test bed and completed 25,000 miles on the road. Actually one engine, after running in, was subjected to a ‘400 hour Endurance Test’ which started on 11 Jan 1972 and was completed on 11 Feb 1972. This gruelling test was the equivalent of running on the road for 26,000 miles with the engine running at full throttle and full load for over half of the time. The full test comprised of 69 cycles (each of 5 hours 50 minutes duration). During each of these cycles the engine speed and load was varied as follows:

Why was it so important to the Harry Webster – The leather patch king of BL – that the engine should not be capable of being bored or stroked? Deliberately removing any future proofing from this critical and expensive component almost sounds like some sort of industrial sabotage!

The following is admittingly my very limited conjecture though perhaps it is related to unrealised plans to develop 4-cylinder versions of the PE166 6-cylinder to replace the Triumph Slant-4, a 4-cylinder version of the 2.3 SD1 Six for example would displace around 1566cc.

However while the H/K-Series prototype units were all-new designs, given the PE166 was loosely derived from the Triumph I6 OHV. It brings up the question of to what degree were the H/K-Series engines loosely derived from the 803-1493cc Triumph 4-cylinder OHV engines or at least influenced by Triumph thinking (apart from retaining a form of BMC’s in-sump transmission layout)?

Would definitely agree regarding the brief of preventing further enlargement beyond 1300cc as being a mistake with the K-Series prototype engine, particularly since the Supermini opposition were moving towards 1400-1600cc engines (and had it reached production there is little certainty a PE166-based 1566cc 4-cylinder unit would have even fitted into ADO74).

This basic essence of this design of course DID make it into production – as the Peugeot/Citroen “suitcase” engine – as found in the 104/Citroen LN/Talbot Samba and the early 205s. Almost identical in fact, with the engine canted so far back at an angle, and the gearbox sort of on the side. Proof that in Britain we’re good at coming up with the initial idea, but lousy at following it through.

Think it may have been, but obviously 1.5 was as small as it ever got. I think there has been few cases where manufacturers have succeeded in building a truly “scalable” engine that can be both very small and very large. Trouble is at lower cubic capacities, you still have a big heavy engine displacing a small capacity so they end up offering little or no economy advantage over an engine that’s designed to be small in the first place. Ford for instance tried it twice and failed….

– Ford CVH; designed to go as low as 1.1 litres but this capacity was dropped when they found out that it wasn’t any more economical than the old 1.1 Kent/Valencia engine yet was more expensive to build.

– Ford Zeta/Zetec – again it was designed to be as small as 1.4 litres, but never got this low.

But in essence most European manufacturers of that era seemed to use two engine families in a ‘small’ and a a ‘large’ format to cover the entire 1.0-2.0 size range – some examples:

Remember the old Alfa DOHC four from the Sixties?
Originally designed as a 1.6 it was downsized to a 1.3 which was never as lively or well loved as its predecessor that was designed as a truly phenomenal 1.3.
Later it was bored and stroked to 1.75 which was a very racy engine with some durability and reliablity problems. Taking strange measures like asymmetrical conrods to move cylinder bores further apart it was increased to 2.0 which was the least pleasing iteration, unwilling to rev and with NVH problems when compared to its smaller siblings.

When was the A series OHC built? About 25 years ago I bought an O series 16v twin cam which I ran in an MG Maestro, the chap I bought it from not only had a few of these but also quite a few A series OHC engines. Were these originally intended for the metro?

The Peugeot engine laid flat was a fantastic pice of packaging, but it was a pain to work on.My brother’s 104 was pretty long in the tooth by the time we had it so had it’s issues. We became well versed with it while he had it, but it lasted longer than the rotbox Metro he replaced it with.

Minor services were easy enough, but anything major was an engine out. With one working on top and one below,we could have the entire engine and gearbox sitting in front of the car in 40 minutes using just our basic facilities at the roadside.

As was the case with a lot of French cars of the time, the spare wheel sat on top of the engine was well. That couldn’t have done the rubber any good!

The H and K engines would have probably gone over budget, when British Leyland was at its most cash strapped, so keeping the venerable A engine and upgrading it to the A plus made sense at the time. I do remember the engine being premiered in the Ital, and the improvements in economy, performance and refinement were considerable over the A series Marina. Also in the Metro, the 1275cc A plus endowed even non MG versions with a top speed of nearly 100 mph, excellent for the time, and economy over 40 mpg.